In the web interface only, new 'short' track name part context. This

In the web interface only, new 'short' track name part context.  This
is the same as 'display' but truncated to short_display glyphs.

playing, recent and new now use this to bound the width of columns in
their tables.  Hover over the truncated names to see the full name (in
a TITLE attribute).

As part of this, rewrote the unicode support.  Everything is now done
via unidata.h/c, which are generated by the new scripts/make-unidata
from UnicodeData.txt (which is not included; get the latest version
from unicode.org instead if you need to update these files).  The
result is both simpler and probably also faster, although it uses more
(immutable) memory.